1. Field of the Invention
The invention refers to a contrivance for automatic rope length correction for a traction rope in an operating mechanism and, in particular, to a window lifter for a motor vehicle side window.
2. Description of the Related Art
A contrivance of this type for automatic rope length correction is shown in DE 31 01 498 A1. It describes a contrivance for the extension of the flexible tube of a Bowden cable. In this well-known contrivance, an end fitting sits firmly affixed on a Bowden tube; on the side turned away from the flexible tube, the fitting is equipped with a spring-mounted tongue that has a lock catch with one slanted and one vertical flank and that is directed towards the rope. A guide bushing that is fixed in place on the side pointing away from the end fitting is pushed onto the rope. Within the section of the lock catch, the guide bushing is equipped with a corresponding tooth system that the lock catch engages with through spring action. The slanted areas on the lock catch and on the tooth system are arranged in such a way that the end fitting and the guide bushing can be pulled apart only while any movement towards each other is blocked. A pressure spring that automatically pushes the elements apart when the rope of the Bowden cable lengthens is located between the end fitting and the guide bushing. Any such lengthening is thereby automatically corrected by an automatic lengthening of the flexible tube within the contrivance.
However, with the known contrivance for automatic rope length correction there remains the problem that temperature-related lengthenings of the rope, i.e. any lengthenings due to temperature fluctuations in the rope material, are also completely compensated under certain conditions, and undesired high tensions in the traction rope result during the subsequent reversal of the lengthening.